/* -*- c++ -*- */
/*
 * Copyright 2008,2010,2012 Free Software Foundation, Inc.
 *
 * This file is part of GNU Radio
 *
 * GNU Radio is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3, or (at your option)
 * any later version.
 *
 * GNU Radio is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with GNU Radio; see the file COPYING.  If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street,
 * Boston, MA 02110-1301, USA.
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include "additive_scrambler_bb_impl.h"
#include <gnuradio/io_signature.h>

namespace gr {
namespace digital {

additive_scrambler_bb::sptr additive_scrambler_bb::make(int mask,
                                                        int seed,
                                                        int len,
                                                        int count,
                                                        int bits_per_byte,
                                                        const std::string& reset_tag_key)
{
    return gnuradio::get_initial_sptr(new additive_scrambler_bb_impl(
        mask, seed, len, count, bits_per_byte, reset_tag_key));
}

additive_scrambler_bb_impl::additive_scrambler_bb_impl(int mask,
                                                       int seed,
                                                       int len,
                                                       int count,
                                                       int bits_per_byte,
                                                       const std::string& reset_tag_key)
    : sync_block("additive_scrambler_bb",
                 io_signature::make(1, 1, sizeof(unsigned char)),
                 io_signature::make(1, 1, sizeof(unsigned char))),
      d_lfsr(mask, seed, len),
      d_count(reset_tag_key.empty() ? count : -1),
      d_bytes(0),
      d_len(len),
      d_seed(seed),
      d_bits_per_byte(bits_per_byte),
      d_reset_tag_key(pmt::string_to_symbol(reset_tag_key))
{
    if (d_count < -1) {
        throw std::invalid_argument("count must be non-negative!");
    }
    if (d_bits_per_byte < 1 || d_bits_per_byte > 8) {
        throw std::invalid_argument("bits_per_byte must be in [1, 8]");
    }
}

additive_scrambler_bb_impl::~additive_scrambler_bb_impl() {}

int additive_scrambler_bb_impl::mask() const { return d_lfsr.mask(); }

int additive_scrambler_bb_impl::seed() const { return d_seed; }

int additive_scrambler_bb_impl::len() const { return d_len; }

int additive_scrambler_bb_impl::count() const { return d_count; }

int additive_scrambler_bb_impl::_get_next_reset_index(int noutput_items,
                                                      int last_reset_index /* = -1 */)
{
    int reset_index =
        noutput_items; // This is a value that gets never reached in the for loop
    if (d_count == -1) {
        std::vector<gr::tag_t> tags;
        get_tags_in_range(
            tags, 0, nitems_read(0), nitems_read(0) + noutput_items, d_reset_tag_key);
        for (unsigned i = 0; i < tags.size(); i++) {
            int reset_pos = tags[i].offset - nitems_read(0);
            if (reset_pos < reset_index && reset_pos > last_reset_index) {
                reset_index = reset_pos;
            }
        }
    } else {
        if (last_reset_index == -1) {
            reset_index = d_count - d_bytes;
        } else {
            reset_index = last_reset_index + d_count;
        }
    }
    return reset_index;
}

int additive_scrambler_bb_impl::work(int noutput_items,
                                     gr_vector_const_void_star& input_items,
                                     gr_vector_void_star& output_items)
{
    const unsigned char* in = (const unsigned char*)input_items[0];
    unsigned char* out = (unsigned char*)output_items[0];
    int reset_index = _get_next_reset_index(noutput_items);

    if (d_count >= 0) {
        for (int i = 0; i < noutput_items; i++) {
            unsigned char scramble_byte = 0x00;
            for (int k = 0; k < d_bits_per_byte; k++) {
                scramble_byte ^= (d_lfsr.next_bit() << k);
            }
            out[i] = in[i] ^ scramble_byte;
            d_bytes++;
            if (i == reset_index) {
                d_lfsr.reset();
                d_bytes = 0;
                reset_index = _get_next_reset_index(noutput_items, reset_index);
            }
        }
    } else {
        for (int i = 0; i < noutput_items; i++) {
            // Reset should occur at/before the item associated with the tag.
            if (i == reset_index) {
                d_lfsr.reset();
                d_bytes = 0;
                reset_index = _get_next_reset_index(noutput_items, reset_index);
            }
            unsigned char scramble_byte = 0x00;
            for (int k = 0; k < d_bits_per_byte; k++) {
                scramble_byte ^= (d_lfsr.next_bit() << k);
            }
            out[i] = in[i] ^ scramble_byte;
            d_bytes++;
        }
    }

    return noutput_items;
}

} /* namespace digital */
} /* namespace gr */
